Method for inspecting input shaft of power steering system

ABSTRACT

Provided is a machine and a method for inspecting an input shaft of a power system. First an second cameras take a photograph of first and second champer of the input shaft from directions perpendicular to the chamfers to capture image data of the chamfers. The input shaft is rotated by an indexing drive until overlapping a central line of first and second chamfers of an input shaft on a standard line of image array coordinate system of a computer. Then, widths of the first and second chamfers of the input shaft is calculated. Thereafter, the indexing drive rotates the input shaft by predetermined degrees. The computer processes image data of another first and second chamfers captured by the first and second cameras and calculates widths of the another first and second chamfers. Continuously, widths of remaining chamfers of the input shaft are calculated.

TECHNICAL FIELD

The present invention relates to a machine and method for inspecting aninput shaft for use in a power steering system of an automobile, whereinthe machining precision of the input shaft for use in the power steeringsystem can be accurately inspected.

BACKGROUND ART

As is well known in the art, the power steering system of an automobileis an apparatus for supplying steering oil to a power cylindercooperating with the steering system by an oil pump driven by enginepower so as to facilitate operating a steering wheel. The power steeringsystem is designed in such a manner that large hydraulic pressure isproduced when parking or driving a car at a low speed, whereas smallhydraulic pressure is produced therein to secure safety when driving acar at a high speed.

An example of such a power steering system will be described withreference to FIGS. 1 and 2. Referring to these figures, a valve body 11is mounted within a valve housing 10, and a port 12 and an oil groove 13forming an oil passage for steering oil are formed on the outer surfaceof the valve body 11 so that they communicate with each other. An inputshaft 20, which is connected to a steering column and rotated inresponse to the operation of the steering wheel, is mounted on the innerside of the valve body 11. A bore 21 is formed at the center of theinput shaft 20, and a plurality of slots 22 are circunmferentiallyformed on the exterior of the input shaft 20 at equal intervals. Ports23, which communicate with the port 12 of the valve body 11 to becomethe oil passage for the steering oil, are formed in the slots 22 of theinput shaft 20, respectively. Further, a torsion bar 14 is mounted inthe bore 21 of the input shaft 20 and is connected to a gear unit 15.

In the meantime, when a driver operates the steering wheel, the inputshaft 20 connected to the steering column is rotated in response to theoperating direction of the steering column so as to control the oilpassage for the steering oil. Accordingly, the operation of the powercylinder is controlled, and thus, the steering of the car is performed.However, a shock is generated due to the sudden variation in anddisturbance of flow of the steering oil which passes at high speed andpressure through the port 12 of the valve body 11 and the ports 23 ofthe input shaft 20 when the direction of rotation of the input shaft 20is changed, while another shock is generated due to physical frictionbetween the input shaft 20 and the steering oil. These shocks becomesources of noise and vibration. Further, wear on the valve body 11 andthe input shaft 20 is produced, and thus, the life of valve body 11 andthe input shaft 20 is shortened. Accordingly, some problems involvedwith a reduction in reliability may be produced.

In order to reduce the hydrodynamic and mechanical shock produced inresponse to a change in the direction of the input shaft 20, the surfaceof the input shaft 20 should be precisely machined. Moreover, right andleft ends of the slots 22 are chamfered so as to reduce fluid resistanceexerted thereon. Chamfered faces at the right and left ends of the slots22, i.e. chamfers 24 specifically shown in FIG. 2, become elements whichgreatly influence the reduction of fluid resistance. Thus, the chamfers24 are precisely machined by using an edge-grinding machine.

In general, the machining precision of the chamfers of the input shaftfor use in power steering systems is performed by means of a samplinginspection through a visual inspection of an inspector. However, visualinspections that relied entirely upon the determination of the inspectormay vary greatly according to measuring errors inherent to therespective inspectors. Thus, there is a problem in that time andmanpower are greatly consumed. In particular, the sampling inspection isinvolved with a problem in that reliability for all the input shaftscannot be completely guaranteed. Therefore, a total inspection for theinput shafts is required. However, a machine for correctly and rapidlyperforming a total inspection for input shafts has not yet beendeveloped and thus the total inspection of input shafts cannot beperformed using the prior art.

DISCLOSURE OF INVENTION

The present invention is conceived to solve the aforementioned problemsin the prior art. An object of the present invention is to provide amachine and method for inspecting an input shaft for use in a powersteering system, wherein the machining precision of the input shaft ofthe power steering system can be accurately inspected.

Another object of the present invention is to provide a machine andmethod for inspecting an input shaft for use in a power steering system,wherein a total inspection for input shafts can be rapidly andaccurately made by automating a series of inspection processes such asthe feeding, cleaning, sorting, and discharge of the input shafts.

A further object of the present invention is to provide a machine andmethod for inspecting an input shaft for use in a power steering system,wherein data on inspection results for the input shaft can be processedand managed in real time.

According to an aspect of the present invention for achieving theobjects, there is provided a machine for inspecting an input shaft foruse in a power steering system, which has a plurality of slots formed atequal intervals in a circumferential direction thereof and first andsecond chamfers formed at left and right sides of the slots. The machineof the present invention comprises a frame on which cleaning andinspecting positions of the input shaft are provided; a cleaning meansinstalled at the cleaning position on the frame for cleaning the inputshaft, an indexing drive installed at the inspecting position on theframe for causing the input shaft to be stepwise rotated; first andsecond cameras for photographing the first and second chamfers of theinput shaft, which is rotated by the indexing drive, in a directionnormal to each of the first and second chamfers and outputting imagedata of the chamfers, respectively; first and second illumination meansfor illuminating the first and second chamfers of the input shaftcoaxially with optical axes of the first and second cameras,respectively; and a computer for processing the image data outputtedfrom the first and second cameras by means of a computer program.

According to another aspect of the present invention, there is alsoprovided a method for inspecting an input shaft for use in a powersteering system, which has a plurality of slots formed at equalintervals in a circumferential direction thereof and first and secondchamfers formed at left and right sides of the slots. The method of thepresent invention comprises the steps of cleaning foreign substancesadhering to the input shaft by means of a cleaning means installed at acleaning position; loading the input shaft from the cleaning positioninto an inspecting position; causing first and second cameras tophotograph the first chamfer in an initial slot and the second chamferin another slot of the input shaft, which is loaded at the inspectingposition, in a direction normal to each of the first and second chamfersto acquire image data of the first and second chamfers, respectively;processing the respective image data of the first and second cameras bymeans of a computer program and overlapping a central line between leftand right edge lines of the first or second chamfer with a standard lineof an image array coordinate system; calculating distances between theleft and right edge lines of the first and second chamfers in anoverlapped state and then calculating width values of the first andsecond chamfers; calculating width values of all remaining first andsecond chamfers while stepwise rotating the input shaft repeatedly by apredetermined angle; and determining whether the input shaft is superioror inferior based on the calculated width values of the first and secondchamfers.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view illustrating an example of an input shaft foruse in a general power steering system;

FIG. 2 is a sectional view taken along line I-I in FIG. 1;

FIG. 3 is a front view showing a configuration of a machine forinspecting the input shaft according to the present invention;

FIG. 4 is a side view showing a configuration of a portion of themachine for inspecting the input shaft according to the presentinvention;

FIG. 5 is a front view showing configurations of an indexing drive, atailstock, first and second cameras, and first and second illuminationdevices according to the present invention;

FIG. 6 is a side sectional view showing the configuration of a cleaningdevice according to the present invention;

FIG. 7 is a plan sectional view showing the configuration of thecleaning device according to the present invention;

FIG. 8 is a plan view showing configurations of the first and secondcameras and the first and second illumination devices according to thepresent invention;

FIG. 9 is a view schematically showing the configurations of the firstand second illumination devices according to the present invention;

FIGS. 10 a-10 c are views showing the operation of overlapping right andleft edge lines of the first and second chamfers with an image arraycoordinate system according to the present invention; and

FIGS. 11 a and 11 b are flowcharts illustrating a method for inspectingthe input shaft according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a preferred embodiment of a machine and method forinspecting an input shaft for use in a power steering system accordingto the present invention will be described in detail with reference tothe accompanying drawings.

Referring first to FIGS. 2 and 3, the machine for inspecting an inputshaft 20 according to the present invention is arranged in series with awell-known edge-grinding machine for machining chamfers 24 of the inputshaft 20. A frame 30 constituting the main body of the machine comprisesa worktable 31 on which a cleaning position P1 and an inspectingposition P2 of the input shaft 20 are provided, and an overhead frame 32installed above the worktable 31. A mounting plate 34 is supported byposts 33 and installed below the overhead frame 32. FIG. 3 shows thatthe cleaning position P1 is on the left side of the worktable 31 whereasthe inspecting position P2 is in the middle of the worktable 31 and theoverhead frame 32. However, this is a simple example, and the cleaningand inspecting positions P1 and P2 may be changed to any other positionssuitable for loading and unloading the input shaft 20.

As shown in FIG.2, the input shaft 20 to be inspected by the inspectingmachine of the present invention includes eight slots 22 formed of anequal width at an equal interval of 45 degrees along a circumferentialdirection of the input shaft 20, and sixteen chamfers 24 formed at rightand left ends of the slots 22. The input shaft 20 that has beencompletely subjected to the machining process by an edge grindingmachine is loaded onto the cleaning position P1 and then onto theinspecting position P2 by means of an operation of a robot. The loadedinput shaft 20 is located upright and then cleaned and inspected at thecleaning and inspecting positions P1 and P3, respectively.

Referring to FIGS. 3, 4, 6 and 7, the machine for inspecting the inputshaft according to the present invention includes a cleaning device 40installed at the cleaning position P1 of the worktable 31 for cleaningforeign substances such as chips, oil and dust from the surface of theinput shaft 20. The cleaning device 40 comprises a base plate 41installed at the cleaning position P1 of the worktable 31, a booth 42which is installed onto the base plate 41 to form a purge room 42 a forsurrounding the cleaning position P1 and includes an entrance 42 b forallowing the input shaft 20 to be loaded into the purge room 42 a, and aloading unit 43 for loading and unloading the input shaft 20 through theentrance 42 b of the booth 42. The loading unit 43 includes a carriage44 for loading and transporting the input shaft 20, an air cylinder 45having a cylinder rod 45 a for moving the carriage 44, and a linearmotion guide 46 for guiding the motion of the carriage 44 in a linearmotion. The linear motion guide 46 includes a guide rail 46 a installedon the top surface of the worktable 31, and a slide 46 b installed onthe bottom surface of the carriage 44 so that it can be slid along theguide rail 46 a.

In addition, on the top surface of the carriage 44 is installed a rotaryunit 47 that is supported for allowing the lower end of the input shaft20 to be rotated. The rotary unit 47 includes a bearing housing 47 afixed to the top surface of the carriage 44, a center 47 c that isrotationally mounted to the bearing housing 47 a through a bearing 47 band supports the lower end of the input shaft 20, and a cap 47 d forcovering the bearing housing 47 a. Air nozzles 51 of an air blower 50are installed within the booth 42 so as to remove foreign substancesfrom the input shaft 20 by blowing air and simultaneously allowing theinput shaft 20 to be rotated. Although it has been illustrated in FIGS.6 and 7 that four air nozzles 51 of the air blower 50 are mounted toallow the input shaft 20 to be rotated in a clockwise direction on thefigures, the positions and number of the air nozzles can be changed.Further, in the embodiment of the present invention, the air blower 50may become a hot air blower for blowing hot air to remove oil from thesurface of the input shaft 20.

An air duct 52 for forming an air curtain is formed on the upper side ofthe booth 42 in order to prevent the foreign substances from beingscattered through the entrance 42 b. The air duct 52 includes aplurality of air nozzles 53 for blowing air toward the entrance 42 b ofthe booth 42. The air cylinder 45 and the air duct 52 in the cleaningdevice 40 are connected to an air supply for supplying air thereto. Theair supply may comprise an air compressor and an air controller forcontrolling the supply of air at predetermined pressure. A dustcollector 60 for collecting the foreign substances removed from theinput shaft 20 through air suction is connected to the purge room 42 aof the booth 42. The dust collector 60 includes a suction unit 62connected to the purge room 42 a of the booth 42 via a suction tube 61,and a dust-collecting tank 64 connected to a discharge tube 63 of thesuction unit 62. The suction unit 62 and the dust-collecting tank 64 ofthe dust collector 60 are loaded in a freely movable cart 65.

Referring to FIGS. 3-5, at the inspecting position P2 of the frame 30 isinstalled a driving device for the stepwise rotation of the uprightinput shaft 20 by a predetermined angle. The driving device includes anindexing drive 70 installed on the top surface of the worktable 31, anda tailstock 80 installed below the mounting plate 34 to be aligned withthe indexing drive 70 and movable vertically with respect to the inputshaft 20 to rotationally support the input shaft 20 in cooperation withthe indexing drive 70.

The indexing drive 70 comprises a servomotor 71 for providing a drivingforce capable of causing the input shaft 20 to be rotated stepwise by apredetermined angle, an air chuck 72 mounted to rotate by means of thedriving of the servomotor 71, and a lower center 73 detachably chuckedto the air chuck 72 for supporting the lower end of the input shaft 20.

As specifically shown in FIG. 5, the tailstock 80 comprises a base plate81 fixed vertically to the bottom surface of the mounting plate 34, anair cylinder 82 with a cylinder rod 82 a which is mounted in front ofthe base plate 81, a lifter 83 fixed to the cylinder rod 82 a of the aircylinder 82, and a linear motion guide 84 for guiding the motion of thelifter 83 generated by the air cylinder 82 into a linear motion. Thelinear motion guide 84 comprises a pair of guide rails 84 a mountedvertically in parallel with and in front of the base plate 81, and apair of slides 84 b mounted below the lifter 83 to be slid along theguide rails 84 a. A rotary unit 85 is mounted on the lower end of thelifter 83. The rotary unit 85 comprises a bearing housing 85 a fixed tothe lower end of the lifter 83, an upper center 85 c that isrotationally mounted to the bearing housing 85 a through a bearing 85 band supports the upper end of the input shaft 20, and a cap 85 d forcovering the bearing housing 85 a. The upward and downward motion of thelifter 83 is sensed and controlled by means of a sensing unit 86. Thesensing unit 86 comprises an upper limit sensor 86 a for sensing thehighest position of the lifter 83 and a lower limit sensor 86 b forsensing the lowest position of the lifter 83.

Referring to FIGS. 3, 5, 8 and 9, the machine for inspecting the inputshaft according to the present invention, comprises first and secondcameras 90 and 91 for photographing the chamfers 24 of the input shaft20 standing upright at the inspecting position P2 of the frame 30 andoutputting image data thereof, and first and second illumination devices100 and 101 for allowing the first and second cameras 90 and 91 toeasily capture images of the chamfers 24 by illuminating the chamfers 24so that the first and second cameras 90 and 91 can photograph thechamfers 24 of the input shaft 20. The first and second cameras 90 and91 are arranged to be normal to the chamfers 24 of the input shaft 20.The first camera 90 takes a photograph of a first chamfer 24 a of anyone slot 23, whereas the second camera 91 takes a photograph of a secondchamfer 24 b thereof. In the preferred embodiment of the presentinvention, the first and second cameras 90 and 91 are CCD cameras(charge coupled device cameras) with 640×480 pixels. The first andsecond cameras 90 and 91 are loaded onto a movement stage 92, which inturn finely adjusts the positions of the first and second cameras 90 and91. The constitution and operation of the movement stage 92 aregenerally known in the art, and thus, detailed descriptions thereof willbe omitted herein. The first and second illumination devices 100 and 101illuminate the chamfers 24 of the input shaft 20 coaxially with opticalaxes of the first and second cameras 90 and 91 and cause the images ofthe chamfers 24 to be projected onto the first and second cameras 90 and91.

As shown in FIG. 9, the first and second illumination devices 100 and101 comprise LEDs (light emitting diodes) 100 a and 101 a that serve aslight sources and are arranged to be orthogonal to the optical axes ofthe first and second cameras 90 and 91, collimators 100 b and 101 b forconverting light emitted from the LEDs 100 a and 100 b into parallellight flux, and beam splitters 100 c and 101 c for applying the parallellight flux emerging from the collimators 100 b and 101 b to the chamfers24 of the input shaft 20 through object lenses 90 a and 91 a of thefirst and second cameras 90 and 91 and for projecting the images of thechamfers 24 incident from the object lenses 90 a and 91 a of the firstand second cameras 90 and 91 onto CCD image sensors 90 b and 91 b of thefirst and second cameras 90 and 91, respectively.

Referring again to FIGS. 3 and 4, the machine for inspecting the inputshaft according to the present invention further includes a controller110 for controlling the operations of the cleaning device 40, the airblower 50, the dust collector 60, the indexing drive 70, the tailstock80, the first and second cameras 90 and 91, and the first and secondillumination devices 100 and 101. The controller 110 is installed on theoverhead frame 32 of the frame 30 and provided with a control panel 111on the front surface of the controller 110. The inspector may setfunctions needed for controlling the machine when inspecting the inputshaft by manipulating or operating the control panel 111. The controller110 visually indicates the operating state of the machine for inspectingthe input shaft via a warning lamp 112 mounted onto the top surface ofthe overhead frame 32.

In addition, the image data of the input shaft 20 outputted from thefirst and second cameras 90 and 91 are inputted into a computer 120 inreal time. The computer 120 is equipped with a microprocessor, a monitor121, an output device such as a printer, and an input device such as akeyboard. The computer 120 processes the image data of the input shaft20 inputted from the first and second cameras 90 and 91 by means of aprogram, displays the processed image data onto the monitor 121, andclassifies the input shafts into superior and inferior ones. Thecomputer 120 interfaces with the controller 110 and the robot for thepurpose of controlling the machine for inspecting the input shaftaccording to the present invention. Further, the controller 110 and thecomputer 120 are received within a case 122 installed on the worktable31 of the frame 30. An air conditioner 130 for controlling thetemperature in the inspecting position P2 at a predetermined level isinstalled on the posts 33 of the frame 30. A change of temperature inthe inspecting position P2 can be prevented through temperature controlperformed by the air conditioner 130, and accordingly, the inspectionenvironment within the inspecting position P2 can be maintainedconstant. Thus, the reliability of image data of the input shaft 20acquired from the first and second cameras 90 and 91 can be enhanced.

Hereinafter, a method for inspecting the input shaft using the machinefor inspecting the input shaft for use in power steering systemsaccording to the present invention will be explained with reference toFIGS. 11 a and 11 b.

Referring again to FIGS. 3 and 7 together with FIGS. 11 a and 11 b,while the input shaft inspection machine is on standby, the carriage 44of the cleaning device 40 is positioned outside the booth 42 with theinput shaft 20 not loaded thereon, and the lifter 83 of the tailstock 80is raised. The robot conveys the input shaft 20 from the edge grindingmachine to the inspection machine according to the present invention insuch a manner that the lower end of the input shaft 20 with the slots 22and the chamfers 24 formed therein is aligned in line with the center 47c of the rotary unit 47. After the input shaft 20 is supported at thecenter 47 c of the rotary unit 47, the air cylinder 45 actuates toadvance the cylinder rod 45 a. Accordingly, the carriage 44 is caused tomove linearly by means of the linear motion guide 46 and is moved intothe purge room 42 a, i.e. the cleaning position P1, through the entrance42 b of the booth 42. The air cylinder 45 stops operating, and theloading process for the input shaft 20 is then completed (S200).

Next, the air blown through the air nozzles 51 of the air blower 50removes foreign substances from the contaminated surface of the inputshaft 20 (S202). At this time, a rotational moment is imparted to theinput shaft 20 by means of force of the air blown through the airnozzles 51 of the air blower 50, and the center 47 c for supporting theinput shaft 20 can be rotated via the bearing 47 b of the rotary unit47. Thus, since the input shaft 20 and the center 47 c can be rotatedtogether, foreign substances on the entire surface of the input shaft 20can be completely removed. As a result, when the first and secondcameras 90 and 91 photograph the chamfers 24 of the input shaft 20 tocapture image data of the chamfers 24, any errors resulting from theforeign substances can also be avoided. The air supplied to air duct 52by means of the air supply is blown to the entrance 42 a of the booth 42through the air nozzles 53, and thus, an air curtain is formed aroundthe entrance 42 a. The foreign substances removed from the surface ofthe input shaft 20 cannot pass through the entrance 42 a of the booth 42by means of the air curtain. Therefore, the inspection machine,including the first and second cameras 90 and 91 located near theinspecting position P2, can be prevented from being contaminated.

Further, the suction unit 62 of the dust collector 60 is actuated at thesame time the air blower 50 of the cleaning device 40 cleans the inputshaft 20. The suction unit 62 sucks in air containing foreign substancesfrom the purge room 42 a of the booth 42 through the suction tube 61 andthen pumps the air into the dust-collecting tank 64 through thedischarge tube 63. In the dust-collecting tank 64, the foreignsubstances are filtered from the air using a filter and collectedtherein, whereas the air is discharged to the outside. After thecleaning of the input shaft 20 has been completed, the air cylinder 45is actuated to move back the cylinder rod 45 a. Then, the carriage 44 iscaused to move linearly by means of the linear motion guide 46 and isagain moved to the initial position through the entrance 42 b of thebooth 42.

Referring to FIG. 5, the robot picks up the input shaft 20 supported bythe center 47 c of the rotary unit 47 and then loads the input shaft 20in such a manner that the lower end of the input shaft is aligned withthe lower center 73 of the indexing drive 70 (S204). After the inputshaft 20 is supported by the lower center 73 of the indexing drive 70,the air cylinder 82 of the tailstock 80 is actuated to advance thecylinder rod 82 a. Accordingly, the lifter 83 is caused to move linearlyand downwardly by means of the linear motion guide 84. Due to thelowering of the lifter 83, the upper center 85 c of the rotary unit 85is aligned with the upper end of the input shaft 20 and supports theinput shaft 20. The input shaft 20 is vertically aligned at theinspecting position P2 by means of the lower center 73 of the indexingdrive 70 and the upper center 85 c of the tailstock 80 (S206). The robotthat completes loading the input shaft 20 into the inspecting positionP2 conveys the following input shaft 20 from the edge-grinding machineto the cleaning position P1 and performs the cleaning of the input shaft20.

The first and second illumination devices 100 and 101 illuminate theinput shaft 20 that is loaded in the inspecting position P2 of theworktable 31 coaxially with the optical axes of the first hand secondcameras 90 and 91 and also project the images of the chamfers 24 of theinput shaft 20 onto the first and second cameras 90 and 91 which in turnphotograph the input shaft 20 and output the image data thereof,respectively (S208). At this time, as shown in FIG. 9, the light emittedfrom the LEDs 100 a and 101 a of the first and second illuminationdevices 100 and 101 is irradiated onto the input shaft 20 through thecollimators 100 b and 101 b, the beam splitters 100 c and 101 c, and theobject lenses 90 a and 91 a of the first and second cameras 90 and 91,respectively. Then, the images of the chamfers 24 of the input shaft 20are projected onto and photographed by the CCD image sensors 90 b and 91b via the object lenses 90 a and 91 a of the first and second cameras 90and 91, and the beam splitters 100 c and 101 c, respectively. The firstcamera 90 takes a photograph of the first chamfer 24 a of any one slot22 of the input shaft 20 in a direction normal to the longitudinaldirection of the input shaft and outputs the relevant image data,whereas the second camera 91 photographs the second chamfer 24 b of theother slot 22 of the input shaft 20 in a direction normal to thelongitudinal direction of the input shaft and outputs the relevant imagedata. The image data of the first and second chamfers 24 a and 24 b ofthe input shaft 20, which are outputted from the first and secondcameras 90 and 91, respectively, are inputted into the computer 120 inreal time.

When it is determined that the image data of the first and secondchamfers 24 a and 24 b have not been inputted into the computer 120 fromthe first and second cameras 90 and 91, the computer 120 causes theservomotor 71 to actuate and the input shaft 20 to be stepwise rotatedby a predetermined angle, e.g. 3 degrees, in response to the output ofcontrol signals (S212). Then, it goes into the above step S208.Thereafter, it is again determined whether the image data of the firstand second chamfers 24 a and 24 b have been inputted into the computer120 by means of the first and second cameras 90 and 91, respectively.The image data of the first and second chamfers 24 a and 24 b can alsobe acquired through the repetitive execution of steps S208 to S212.

If the image data of the first and second chamfers 24 a and 24 b areacquired through the execution of the above processes, the computer 120causes a gray level image of any one of the first and second chamfers 24a and 24 b, e.g. the first chamfer 24 a, to be binary coded by means ofa threshold and obtains left and right contours from the binary image ofthe first chamfer 24 a (S214). Next, through the least square errormethod, relevant noise is filtered out to obtain linear equations of theleft and right contours, and left and right edge lines 24 a-1 and 24 a-2are calculated (S216). The computer 120 displays the left and rightedgelines 24 a-1 and 24 a-2 of the first chamfer 24 a onto the monitor121 and determines whether a central line between the left and rightedge lines 24 a-1 and 24 a-2 overlaps with a standard line 141 of animage array coordinate system 140 (S218). FIGS. 10 a and 10 b show thatthe central line of the left and right edge lines deviates from thestandard line 141 of the image array coordinate system 140.

When it is determined that the central line of the left and right edgelines 24 a-1 and 24 a-2 does not overlap the standard line 141 of theimage array coordinate system 140, the computer 120 causes theservomotor 71 to actuate and the input shaft 20 to be stepwise rotatedby a predetermined angle, e.g. 1 degree, in response to the output ofthe control signals, as shown in FIG. 10 c. Through the repetitiveexecution of steps S214 to S220, the central line of the left and rightedge lines 24 a-1 and 24 a-2 is caused to overlap with the standard line141 of the image array coordinate system 140. It is determined in thepreferred embodiment of the present invention that the central line ofthe left and right edge lines 24 a-1 and 24 a-2 has overlapped with thestandard line 141 of the image array coordinate system 140 if the formeroverlaps with the latter within a predetermined error range of 20 μm,for example.

In the meantime, if it is determined that the central line of the firstleft and right edge lines 24 a-1 and 24 a-2 overlaps the standard line141 of the image array coordinate system 140, the computer 120 firstcalculates distances between the left edge lines 24 a-1 and 24 b-1 andthe right edge lines 24 a-2 and 24 b-2 of the first and second chamfers24 a and 24 b, respectively. Then, the computer 120 calculates andstores a width value of the initial first and second chamfers 24 a and24 b based on the calculated distances (S222). The computer 120calculates the width value of the initial first and second chamfers 24 aand 24 b and then causes the servomotor 71 to actuate and the inputshaft 20 to be stepwise rotated by a predetermined angle, e.g. 45degrees, in response to the output of the control signals. The first andsecond cameras 90 and 91 photograph the next first and second chamfers24 a and 24 b so as to acquire the image data of the next first andsecond chamfers 24 a and 24 b (S224). In the same manner as describedabove, the computer 120 causes the gray level images of the first andsecond chamfers 24 a and 24 b inputted from the first and second cameras90 and 91 to be binary coded by means of a threshold, through the givenprogram. Then, the computer obtains the left and right contours from thebinary images of the first and second chamfers 24 a and 24 b. Further,through the least square error method, noise is filtered out to obtainthe linear equations of the left and right contours for the respectivefirst and second chamfers 24 a and 24 b; left edge lines 24 a-1 and 24b-1 and the right edge lines 24 a-2 and 24 b-2 are then obtained.Thereafter, the distances between the left edge lines 24 a-1 and 24 b-1and the right edge lines 24 a-2 and 24 b-2 of the first and secondchamfers 24 a and 24 b are calculated, and the width value of the nextfirst and second chamfers 24 a and 24 b is then calculated and stored(S226).

Next, the computer 120 determines whether the width values of the firstand second chamfers 24 a and 24 b have been obtained a predeterminednumber of times (S228). In the preferred embodiment of the presentinvention, the respective eight values are obtained as width values ofthe first and second chamfers 24 a and 24 b. If it is determined thatthe width values of first and second chamfers 24 a and 24 b have not yetbeen obtained eight times, it goes into step S224 and the computer 120subsequently calculates the width values of the remaining first andsecond chamfers 24 a and 24 b. Thus, the width values of all the firstand second chamfers 24 a and 24 b can be calculated through theexecution of the above steps.

The computer 120 calculates width values of the slots 22 using the widthvalues of the first and second chamfers 24 a and 24 b and givencalculation formula (S230), and also calculates total width valuesobtained by adding the width values of the slots 22 and the width valuesof the first and second chamfers 24 a and 24 b (S232). The computer 120determines whether the input shafts are superior or inferior based onthe calculated width values of the slots 22, the total width values, andthe width values of the first and second chamfers 24 a and 24 b (S234).To this end, it is determined whether the machining precision of theslots 22 and the chamfers 24 is within an allowable and predeterminederror range. As a result, the input shafts satisfying the precisionrequirement are classified as superior, whereas the remaining inputshafts are classified as inferior (S234). Although the method forinspecting whether the input shafts are superior or inferior based onthe calculated widths of the slots 22 and the chamfers 24 has beendescribed above, the inspection whether the input shafts are superior orinferior may be accomplished based only on the machining precision ofthe chamfers 24 as well.

Finally, when the air cylinder 82 of the tailstock 80 is actuated tomove back the cylinder rod 82 a after the classification of the inputshafts 20 has been completed, the lifter 83 moves linearly and is raisedby means of the linear motion guide 84. The robot unloads, from theinspecting position P2, the superior input shafts 20 onto a superiorgoods conveying line (S236) and the inferior input shafts 20 onto aninferior goods conveying line (S238). The robot loads the followinginput shaft 20 into the inspecting position P2 and then causes theprocess of inspecting an input shaft to be repeated.

The above description has been merely used to explain the preferredembodiment of the present invention, and the scope of the presentinvention is not limited to the preferred embodiment described herein.It is apparent to those skilled in the art that various changes,modifications and substitutions thereto can be made within the technicalspirit and the scope of the present invention defined by the appendedclaims. It should be understood that such a preferred embodiment fallswithin the scope of the present invention.

INDUSTRIAL APPLICABILITY

According to a machine and method for inspecting an input shaft for usein a power steering system of the present invention described above, themachining precision of the input shafts having a plurality of slots andfirst and second chamfers formed at the left and right ends of the slotscan be accurately inspected by causing the first and second cameras tophotograph the input shaft and processing the obtained image datathrough a computer program. Further, a series of inspection processessuch as the feeding, cleaning and classification of the input shafts canbe automated. Thus, a total inspection for input shafts can be rapidlyand correctly made. Furthermore, there is an advantage in thatinspection data for input shafts can be processed and managed in realtime.

1. A method of inspecting an input shaft for use in a power steeringsystem, said method comprising the steps of: providing said input shaftwhich has a plurality of slots formed at equal intervals in acircumferential direction thereof and first and second chamfers formedat left and right sides of the slots; cleaning foreign substancesadhering to the input shaft at a cleaning position; loading the inputshaft from the cleaning position into an inspecting position; causingfirst and second cameras to photograph the first chamfer in an initialslot and the second chamfer in another slot of the input shaft, which isloaded at the inspecting position, in a direction normal to each of thefirst and second chamfers to acquire image data of the first and secondchamfers, respectively; processing the respective image data of thefirst and second cameras by means of a computer program and overlappinga central line between left and right edge lines of the first or secondchamfer with a standard line of an image array coordinate system;calculating distances between the left and right edge lines of the firstand second chamfers in an overlapped state and then calculating widthvalues of the first and second chamfers; calculating width values of allremaining first and second chamfers while stepwise rotating the inputshaft repeatedly by a predetermined angle; and determining whether theinput shaft is superior or inferior based on the calculated width valuesof the first and second chamfers.
 2. The method as claimed in claim 1,wherein left and right contours are obtained from binary images obtainedby causing gray level images to be binary coded by means of a threshold,and the left and right edge lines of the first and second chamfers arethen calculated from linear equations of the left and right contours. 3.The method as claimed in claim 1, further comprising the step ofcalculating width values of the slots based on the distances between theleft and right edge lines of the first and second chamfers.